The NIS (NEON Imaging Spectrometer) is an airborne pushbroom hyperspectral instrument developed by NASA Jet Propulsion Laboratory (JPL) for the National Ecological Observation Network (NEON) and is included in all three of NEON’s Airborne Observation Platform (AOP) payloads. NEON, funded by the National Science Foundation (NSF), is a continental-scale observatory designed to collect long-term data to better understand and forecast impacts of climate change, land use change and invasive species (Kampe et al. 2010). NEON has recently completed the construction phase and is in the initial operational phase, which represents annual activities that will be repeated for the remaining 30-year lifetime of the project (Goulden et al. 2019). The AOP begun data collection in 2013, although only a small subset of NEON sites was collected. By 2018 and 2019, AOP was collecting data in 16 domains annually, representing the typical data collection scenario during the operational phase of the NEON project. NEON provides 28 data products from AOP, which are publicly available and can be freely accessed from NEON data portal: https://data.neonscience.org/home. In addition to the NIS, AOP payloads include a discrete and full-waveform lidar and a high resolution RGB camera. The NIS design is based on AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) NextGen Imaging Spectrometer and measures radiant energy both in VNIR (Visible-Near Infrared) and SWIR (Shortwave Infrared) spectral region (380-2510 nm) with ~5 nm sampling and 1 mRad instantaneous field of view (IFOV) (Kuester et al. 2010). This 1 mRad IFOV leads to a ground resolution of 1m at a typical flight altitude of ~1000m. In order to ensure the accuracy of the measurements, the NIS requires stable and consistent annual calibrations (Leisso et al. 2014). Assessment of NIS calibration datasets revealed anomalies that should be characterized and corrected to improve the accuracy of NIS datasets. This presentation will briefly discuss the current status of NEON project and provides detailed description of NIS calibration improvements including: 1) characterizing NIS stray light anomalies, 2) techniques implemented to correct such anomalies, and 3) NIS stability analysis. Goulden T., B. Hass, J. Musinsky, and A. K. Shrestha, 2019, "Status of NEON's Airborne Observation Platform", AGU Fall Meeting, 9-13 December, 2019, San Francisco, CA, USA, Kampe T. U., B. R. Johnson, M. Kuester, and M. Keller, 2010, "NEON: the first continental-scale ecological observatory with airborne remote sensing of vegetation canopy biochemistry and structure", Journal of Applied Remote Sensing 4(1), 043510 (1 March 2010). https://doi.org/10.1117/1.3361375 Kuester M. A., J.T. McCorkel, Johnson, B.R., and Kampe T.U., 2010, "Radiometric Calibration Concept of Imaging Spectrometers for a long-term Ecological Remote Sensing Project" Leisso N., Kampe T., Karpowicz B., 2014, "Calibration of the National Ecological Observatory Network's airborne imaging spectrometers", 2014 IEEE Geoscience and Remote Sensing Symposium, Quebec City, QC, 2014, pp. 2625-2628. doi: 10.1109/IGARSS.2014.6947012